You don't specify the technology. Answers for TTL and CMOS are slightly different, and there are quite a few others as well. You also don't specify an objective for what you call "better".
Short of the technology in question, the only facet of the answer you can specify is that you need to connect unused inputs either to something interpreted as logical 1 (or the output will get fixed at logical 1 irrespective of the input) or to the input to be inverted.
Which kind of input that is interpreted as logic 1 will be best depends on the technology. Some will take VCC directly, some may warrant a resistor for protection against transient behavior. While I wouldn't fancy it, TTL logic would not mind open pins a lot, either.